1. Technical Field of the Invention
The present invention relates to novel non-aerosol self- or artificial/sunless tanning foams that incorporate a judiciously selected surfactant, sodium coco-sulfate, which augments foam quality and which enhances both visual and self-tanning agent stability.
This invention also relates to a regime or regimen for the artificial/sunless tanning of human skin by topically applying thereon, for such period of time as required to elicit the desired self-tanning effect, a stable cosmetic/dermatological foaming composition comprising an artificial/sunless tanning agent, most notably dihydroxyacetone (xe2x80x9cDHAxe2x80x9d), and the surfactant sodium coco-sulfate, formulated into a topically applicable, cosmetically/dermatologically acceptable vehicle, diluent or carrier therefor.
2. Description of the Prior Art
It is known to this art that non-aerosol self-tanning foams are difficult and problematic to formulate because of the sensitivity of, for example DHA, to amine functional groups. Nonetheless, amine functions are present in almost all of the commercially available surfactants. And this is the reason there are but very few non-aerosol self-tanning foams available on the commercial market.
Indeed, one such commercially available non-aerosol self-tanning foam contains a DHA-compatible surfactant. To the contrary, however, visual stability issues (sedimentation) developed within 1-3 weeks after formulation at 5xc2x0 C., 25xc2x0 C., 37xc2x0 C. and 45xc2x0 C.
Oil-in-water stable emulsions (but not foams) are also known to this art which contain the self-tanning agent DHA in combination with a stabilizing amount of the sunscreen, octyl dimethyl PABA. Compare U.S. Pat. No. 4,434,154 to McShane. Cf. U.S. Pat. No. 3,177,120 to Black et al.; DE 19955375 A1.
Accordingly, a major object of the present invention is the provision of novel non-aerosol self- or artificial/sunless tanning foams that incorporate a particular surfactant to date never before included in self-tanning systems, such particular surfactant, sodium coco-sulfate, not only augmenting the foam quality while not degrading, for example the dihydroxyacetone, DHA, but also even enhancing the stability thereof.
This invention thus features formulating a judiciously selected surfactant, sodium coco-sulfate, which does not contain an amine functional group, into non-aerosol artificial/sunless tanning foams to enhance the quality thereof, as well as both visual and DHA stability.
Too, the present invention features a regime or regimen for the artificial/sunless tanning of human skin by topically applying thereon a homogeneous very good quality foam comprising an artificial/sunless tanning agent, characteristically DHA, and the surfactant sodium coco-sulfate, formulated into a topically applicable, cosmetically/dermatologically acceptable vehicle, diluent or carrier therefor.
More particularly according to the present invention, novel non-aerosol self-tanning foams are hereby provided that include a surfactant, sodium coco-sulfate, which does not contain an amine function, which augments foam stability and which enhances both visual and DHA stability.
The DHA stability was especially good. Indeed, after 8 weeks, the DHA loss was determined to be  less than 10% at room temperature (25xc2x0 C.) and  less than 30% at 45xc2x0 C. (as measured via that USTM #132 technique referred to later herein).
Sodium coco-sulfate is the sodium salt of the sulfate ester of coconut alcohol that conforms generally to the formula:
ROSO3Na
wherein R represents the alkyl groups derived from coconut oil. The technical name is sulfuric acid, monococoyl ester, sodium salt. Also, INCI name: sodium coco-sulfate; CAS No. 68955-19-1; EINECS No. 273-257-1.
Sodium coco-sulfate is an infrequently-used surfactant for personal cleansing products, but has never been incorporated into artificial/sunless tanning foams.
Too, sodium coco-sulfate behaves quite differently from the traditional surfactants, representative of which being sodium lauryl sulfate. The following data compare the general differences existing between the two surfactants.
A preferred sodium coco-sulfate according to the present invention is that marketed by McIntyre Group Ltd. as MACKOL(trademark) CAS-100F. It is said to be a special, naturally derived flaked form of sodium coconut oil fatty alcohol sulfate, developed for all natural shampoos and skin cleansing products. It is an easy-to-handle flowable flake, having a low free fatty alcohol content which is said to maximize formulating flexibility.
Its specifications and suggested applications are reported as follows:
SPECIFICATIONS:
APPLICATIONS:
Shampoos
Bath Products
Skin Cleansers
Liquid Dishwash
MACKOL(trademark) CAS-100F is thus marketed as a 90% active granular product by weight, namely, as a unique, naturally derived, granular anionic surfactant for the formulation of xe2x80x9cnatural typexe2x80x9d personal cleansing products.
The approximate composition of MACKOL(trademark) CAS-100F is as follows:
Another specific sodium coco-sulfate according to this invention, albeit less preferred than MACKOL(trademark) CAS-100F, is that anionic alkyl sulfate marketed as Sulfopon(copyright) HC Granulate by Henkel-Cognis; chain length distribution:
Sulfopon(copyright) HC Granulate is a recommended surfactant for the manufacture of hand cleaning pastes, especially for customers who encounter difficulties in terms of handling and processing of FAS pastes due to insufficient equipment.
These white granules are said to be (1) easy to handle, (2) high in active matter content, (3) nearly dustless, (4) a solid with excellent flowability, (5) easy to store over long periods, (6) not prone to hydrolysis, and (7) quickly soluble in warm water at 70xc2x0 C.
The preferred chain length distribution of the sodium coco-sulfate (C12-C18 fatty alcohol sulfate, sodium salt) according to the invention is on the order of:
Such chain length distribution of the surfactant provides both optimal foam quality and stability of the self-tanning system, i.e., finished product homogeneous and foam quality very good.
It has also been determined that the optimal concentration of the sodium coco-sulfate in the subject non-aerosol self-tanning foams is on the order of 3%-4% by weight, more preferably on the order of 3% by weight (2.835% by weight active material). Those compositions containing 3% by weight of sodium coco-sulfate uniformly exhibit good foam quality as well as stability.
The subject artificial/sunless, or self-tanning cosmetic/dermatological compositions of this invention comprise an effective amount of at least one artificial/sunless tanning agent, notably dihydroxyacetone or DHA, for example on the order of 5% by weight.
To date, a wide variety of artificial tanning agents has been developed. Artificial tanners provide the highly sought-after tanning or darkening response once only available through harmful exposure to ultraviolet radiation. DHA, in particular, has been widely utilized in cosmetics to accomplish artificial tanning of the skin. Proteins of the epidermis have a very high concentration of arginine, lysine, and histidine and the reaction of skin with DHA to produce an artificial tan takes advantage of this fact. The tanning reaction proceeds through combination with free amino groups in skin proteins, and particularly by combination of DHA with the free guanido group in arginine.
Preferred among those artificial tanners which are useful in the compositions in the instant invention are those selected from the group comprising: allose, alpha hydroxy substituted ketones such as dihydroxyacetone, altrose, arabinose, erythrose, fructose, galactose, glucose, glyceraldehyde, indoles, lactose, mannose, reose, ribose, pentose, sucrose, tallose, xylose, and mixtures thereof.
Most preferred among those artificial/sunless tanners which are useful in the compositions of the present inventions is dihydroxyacetone. In this respect, it should be appreciated that DHA is not at all easy to formulate, is particularly sensitive and compositions comprised thereof tend to be quite unstable over time, (as DHA tolerates but few raw materials, e.g., carbomers). Thus, the stable formulations according to the invention are all the more unexpected and surprising.
In order to further illustrate the present invention and the advantages thereof, the following specific examples are given, it being understood that same are intended only as illustrative and in nowise limitative.